Needs for improvement of spatial resolution of X-ray CT (computed tomography) devices are increasing with use of more sophisticated X-ray CT measurement techniques. In order to improve the spatial resolution, use of finer X-ray detectors in the X-ray detection module, i.e., use of X-ray detectors of smaller sizes, is contemplated, but it results in degradation of the S/N ratio of the detected signals.
As a method for improving the spatial resolution without using smaller X-ray detectors in the X-ray detection module, a technique called flying focal spot (FFS) method is disclosed in Patent document 1. The FFS method is a method of producing positional shift of X-ray beam by electromagnetically changing the position of the focal point of X-ray alternately between two positions during the rotational movement of the scanner, and doubling the density of X-ray transmission data by that positional shift.
In the FFS method, the projection data specified by the angular direction of the rotational movement of the scanner (also called view direction or θ direction) and the direction of the channel of the X-ray detection module suffer from missing of data for every view direction associated with the alternate change of the position of the X-ray focal point. In conventional techniques, such missing data are interpolated by using actually measured data (also called real data) obtained for the positions on both sides of the missing data position, for example, for the channel direction or the view direction.